A Rationale-based Model for Architecture Design Reasoning

6.1. A conceptual model for design reasoning
Garlan et al. [48] found that conflicting assumptions which are implicit lead to poorquality
system architecture. As it is difficult to draw the line between requirements,
assumptions and constraints [135], we take an all-inclusive approach and conjecture that
missing motivational reasons (including assumptions, constraints and requirements) can
affect the decision making process adversely and can result in inferior design solutions
because of ill-informed decisions.
With motivational reasons come the design issues that need to be resolved to create a
design solution. An architect would resolve the issues by evaluating the relative benefits
and weaknesses of the available options to select the most suitable design. The arguments
and the reasoning are captured as a result of the decision, i.e. the design rationale. To
depict the relationship between motivational reasons, design rational, and design objects,
we present a conceptual model for design process in Figure 6.1, based on which we will
develop the rationale-based architecture model AREL. The conceptual model capturing
design reasoning relies on the distinction between motivational reasons and design rationale.
There are two important aspects of such a conceptual model:
• Entity - it identifies the information that needs to be represented, namely architecture
design rationale and architecture design elements.
• Relationship - it relates the architecture design rationale to the architecture elements
in a structured way to explain how a decision is made and what the outcomes are.
Figure 6.1: An Architecture Rationale Conceptual Model
A motivational reason acts as an input to a decision. It motivates and/or constrains a
decision. A motivational reason should be explicitly represented in an architecture design,
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